To achieve special effects in the fabric or a protective thread intersection or an early or delayed enmeshing or anchoring of the weft thread, it is known to modify, during a weaving operation, the conventional heddle frame movement. In this connection, the conventional heddle frame movement is the simultaneous intersection of all heddle frames and the time of the insertion of a pick with respect to the heddle frame movement.
With changed heddle frame movement, it is desirable first to modify the movement phase in the area of the shed end by having the passage of the warp threads, or a part of the warp threads, through this point take place either earlier or later.
In dobbies various solutions have been used, which are based on the principle of effecting a change from the original heddle frame movement by means of a lever drive, which lever drive resulted in a distortion of such original movement. Instead of the lever drive, sliders have also been used. Such solutions caused considerable deterioration from the optimum acceleration law realized in the original heddle frame movement. The consequence was an increased wear on machines and fabrics. In addition, the additional gear parts resulted in more mass to move, friction and play. Due to the increases of the weaving speeds, better solutions have always been sought, which were used in particular in dobbies with a rotatable drive instead of the reciprocally swinging gears.
The purpose of the invention is to provide simple adjusting means which is exposed to no wear and functions satisfactorily at high speeds.